Wednesday, November 04, 2009

Evidence of tumbaga from the Sipan royal tombs, Peru

Earlier in this blog I mentioned that word tumbaga is used both in the Philippines and across the Pacific in the Americas to refer to a gold-copper alloy.

At one time it was thought that both the word and technology had crossed the seas from the Philippines to the Americas during Spanish times with the trade galleons. Tumbaga involves depletion gilding or electrochemical replacement to make the alloy appear as pure gold on the surface -- on both sides of the Pacific

However, the archaeological evidence clearly shows that tumbaga technology was known in the Americas long before Columbus sailed to America.

An abstract of a recent study (below) of the royal tombs of Sipan in Peru shows that there was evidence of tumbaga among the Moche between between 50 and 700 CE.

Paul Kekai Manansala

Appl Radiat Isot. 2009 Sep 12. [Epub ahead of print]

Pre-Columbian alloys from the royal tombs of Sipán; energy dispersive X-ray fluorescence analysis with a portable equipment.

Cesareo R, Calza C, Dos Anjos M, Lopes RT, Bustamante A, Fabian S J, Alva W, Chero Z L.

Dip. di Matematica e Fisica, Università di Sassari, via Vienna 2, 07100, Sassari, Italy.

On the north coast of present-day Peru flourished approximately between 50 and 700 AD, the Moche civilization. It was an advanced culture and the Moche were sophisticated metalsmiths, so that they are considered as the finest producers of jewels and artefacts of the region. The Moche metalworking ability was impressively demonstrated by the objects discovered by Walter Alva and coworkers in 1987, in the excavations of the "Tumbas Reales de Sipán". About 50 metal objects from these excavations, now at the namesake Museum, in Lambayeque, north of Peru, were analyzed with a portable equipment using energy-dispersive X-ray fluorescence. This portable equipment is mainly composed of a small size X-ray tube and a thermoelectrically cooled X-ray detector. Standard samples of gold and silver alloys were employed for quantitative analysis. It was determined that the analyzed artefacts from the "Tumbas Reales de Sipán" are mainly composed of gold, silver and copper alloys, of gilded copper and of tumbaga, the last being a poor gold alloy enriched at the surface by depletion gilding, i.e. removing copper from the surface.